article · BMC Oral Health
Zirconia crowns are widely used in restorative dentistry, with manufacturing options including traditional subtractive milling and additive three-dimensional printing. An assessment of twenty monolithic zirconia crowns compared the marginal gap and internal fit produced by both fabrication techniques. Measurements taken using the vertical marginal gap technique showed that printed crowns had a wider average marginal opening of 80 micrometres compared to 60 micrometres for milled crowns. Similarly, evaluation through the silicone replica technique recorded marginal gaps of 100 micrometres for printed units and 60 micrometres for milled units. Internal fit evaluations showed significant differences between the two methods across most reference locations, though axial gaps were comparable. While subtractive milling delivers superior precision, additive printing produces crowns that remain within clinically acceptable limits for internal adaptation and marginal fit.
Accurate fit in dental crowns is essential to prevent bacterial leakage, plaque accumulation and restoration failure. Demonstrating that additive manufacturing achieves clinically viable marginal fit reassures dental practitioners and prosthodontists that three-dimensional printing is a viable alternative to conventional milling for producing durable monolithic zirconia restorations.
This research provides applied comparative data relevant to dental laboratories, digital dentistry hardware developers and clinical prosthodontists. Because three-dimensional printed zirconia crowns met clinical acceptability criteria, the method represents a viable alternative to subtractive milling that could reduce material waste. The technology is in an applied and tested state, indicating readiness for clinical consideration alongside existing milling systems.
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BACKGROUND: This study aimed to evaluate and compare the marginal gap using two different methods and the internal fit of 3D printed and zirconia crowns. METHODS: 3Y-TZP zirconia crowns (n = 20) were manufactured using subtractive milling (group M) and 3D printed (group P). The marginal gap was measured at 60 points using vertical marginal gap technique (VMGT). On the other hand, the silicone replica technique (SRT) was used to evaluate the internal fit and was divided into 4 groups: marginal gap, cervical gap, axial gap, and occlusal gap where the thickness of light impression was measured at 16 references. The numerical data was tested for normality using Shapiro-Wilk's test. They were found to be normally distributed and were analyzed using an independent t-test. RESULTS: Using VMGT, group P had significantly higher mean marginal gap values of 80 ± 30 µm compared to group M = 60 ± 20 µm (p < 0.001). Also, with the SRT, the marginal gap of group P (100 ± 10 µm) had significantly higher values compared to group M (60 ± 10 µm). The internal fit showed significant difference between the tested groups except for Axial Gap. CONCLUSIONS: Although milled crowns showed better results. The 3D printed zirconia crowns offer clinically acceptable results in terms of marginal adaptation and internal fit. Both VMGT and SRT are reliable methods for the assessment of the marginal gap.
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DOI: 10.1186/s12903-023-03184-8
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